多线程下载文件

package sss;

import java.io.IOException;
import java.util.Date;

public class test1 {
    public static void main(String[] args) {
            Date startDate = new Date();
            DownloadFileWithThreadPool pool = new DownloadFileWithThreadPool();
            try {
                pool.getFileWithThreadPool("http://mpge.5nd.com/2016/2016-11-15/74847/1.mp3", "D:\\1.mp3", 100);
            } catch (IOException e) {
                e.printStackTrace();
            }
            System.out.println(new Date().getTime() - startDate.getTime());
        }
}

package sss;

import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

//定义线程Pool

public class DownloadFileWithThreadPool {

    public void getFileWithThreadPool(String urlLocation, String filePath, int poolLength) throws IOException {
        ExecutorService threadPool = Executors.newCachedThreadPool();

        long len = getContentLength(urlLocation);
        System.out.println(len);
        for (int i = 0; i < poolLength; i++) {//分成100段
            long start = i * len / poolLength;
            long end = (i + 1) * len / poolLength - 1;
            if (i == poolLength - 1) {
                end = len;
            }
            System.out.println(start+"---------------"+end);
            DownloadWithRange download = new DownloadWithRange(urlLocation, filePath, start, end);
            threadPool.execute(download);
        }
        threadPool.shutdown();
    }

    public static long getContentLength(String urlLocation) throws IOException {
        URL url = null;
        if (urlLocation != null) {
            url = new URL(urlLocation);
        }
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setReadTimeout(50000);
        conn.setRequestMethod("GET");
        long len = conn.getContentLength();

        return len;
    }

}

package sss;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;

public class DownloadWithRange implements Runnable {
    private String urlLocation;

    private String filePath;

    private long start;

    private long end;

    DownloadWithRange(String urlLocation, String filePath, long start, long end) {
        this.urlLocation = urlLocation;
        this.filePath = filePath;
        this.start = start;
        this.end = end;
    }

    @Override
    public void run() {
        try {
            HttpURLConnection conn = getHttp();
            conn.setRequestProperty("Range", "bytes=" + start + "-" + end);

            File file = new File(filePath);
            RandomAccessFile out = null;
            if (file != null) {
                out = new RandomAccessFile(file, "rw");
            }
            out.seek(start);
            InputStream in = conn.getInputStream();
            byte[] b = new byte[1024];
            int len = 0;
            while ((len = in.read(b)) >= 0) {
                out.write(b, 0, len);
            }
            in.close();
            out.close();
        } catch (Exception e) {
            e.getMessage();
        }

    }

    public HttpURLConnection getHttp() throws IOException {
        URL url = null;
        if (urlLocation != null) {
            url = new URL(urlLocation);
        }
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setReadTimeout(50000);
        conn.setRequestMethod("GET");

        return conn;
    }

}